[spirv] Add method to allocate new ID from code buffer.

src/spirv/spirv_code_buffer.cpp

@@ -40,6 +40,16 @@ namespace dxvk {
   }
   
   
+  uint32_t SpirvCodeBuffer::allocId() {
+    constexpr size_t BoundIdsOffset = 3;
+
+    if (m_code.size() <= BoundIdsOffset)
+      return 0;
+
+    return m_code[BoundIdsOffset]++;
+  }
+
+
   void SpirvCodeBuffer::append(const SpirvCodeBuffer& other) {
     if (other.size() != 0) {
       const size_t size = m_code.size();

src/spirv/spirv_code_buffer.h

@@ -76,6 +76,15 @@ namespace dxvk {
       return SpirvInstructionIterator(nullptr, 0, 0);
     }
     
+    /**
+     * \brief Allocates a new ID
+     *
+     * Returns a new valid ID and increments the
+     * maximum ID count stored in the header.
+     * \returns The new SPIR-V ID
+     */
+    uint32_t allocId();
+    
     /**
      * \brief Merges two code buffers
      * 
@@ -101,7 +110,7 @@ namespace dxvk {
      * \param [in] wordCount Number of words
      */
     void putIns(spv::Op opCode, uint16_t wordCount);
-    
+
     /**
      * \brief Appends a 32-bit integer to the buffer
      * \param [in] value The number to add